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Thesis defences

PhD Oral Exam - Rocco Portaro, Mechanical Engineering

Liquid Needle Free Injectors: Design and Analysis of Power Sources

Thursday, August 11, 2022 (all day)

This event is free


School of Graduate Studies


Daniela Ferrer



When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.


Drug delivery without the use of hypodermic needles has been a long-term objective within the medical field. Although there exist many different needle free technologies, these have typically been limited to the delivery of micro-molecules and small volumes. This dissertation focuses on liquid jet injection, a technique utilizing micro size, high-speed liquid jets for the delivery of macro-molecules in line with commercially developed injectables. The devices using this technique are known as needle-free liquid jet injectors (NFJI). However, pain, bruising, hematomas, incomplete delivery, and cross-contamination, have limited their widespread clinical use.

This dissertation will focus on contributing to the development of the most important aspect of an NFJI, the power source. Power source requirements of NFJIs are established through a numerical study utilizing a computational fluid dynamic model constructed by Nakayama et al. (2013) and subsequently analyzing the effect of drug viscosity to underline the requirements for successful liquid jet injection. The results of this study highlight that increasing viscosity to levels required by novel drug therapies will make it difficult for commercially available NFJI to deliver viscous injectables.

These limitations are addressed by the analysis of a servo-tube actuated NFJI, this prototype advanced the work conducted by Taberner et al., (2012) and Do et al., (2017), by utilizing advanced power electronics and fully closed-loop control to illustrate the viability and real-time controllability of linear PMSMs for powering NFJIs. This yielded a prototype device producing accurate pressure profiles and large delivery volumes, however demonstrated slight difficulties in scalability.

In response, a combustion-driven injector was analyzed to provide rapid energy release in a smaller form factor. The study yielded a prototype capable of producing jets attaining stagnation pressures above 80 MPa, by detonating a gaseous mixture of acetylene-oxygen. A model that characterizes the pressure output of the device is also developed and verified experimentally.

A novel NFJI, that combines the scalability and energy release of the combustion-driven injector, with the controllability of a servo tube-powered NFJI is also presented. This concept utilizes a rotary servo motor, electromagnetic clutch and drive screw, to reduce the power requirements at the onset of liquid jet injection while providing real-time control of jet stagnation pressure.

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